Fuse for automobile

ABSTRACT

A fuse for an automobile having a housing manufactured by the injection molding of a polyamide resin composition, wherein the polyamide resin composition constituting the housing has a heat of fusion of 40 J/g or more, as measured by means of a differential scanning calorimeter, and exhibits an average diameter of spherulites of 0.5 μm or less, as measured by the observation by means of a polarization optical microscope.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a fuse for an automobile having ahousing manufactured by the injection molding of a polyamide resincomposition, more specifically, a fuse for an automobile with excellenttransparency, arc and heat resistance, in particular, with transparencythat does not deteriorate even if it is used in the high-temperatureenvironment of the engine room of automobiles.

2. Detailed Description of the Prior Art

Fuses are installed in the circuits of electric components inautomobiles to prevent overcurrents. The numbers of fuses beinginstalled are increasing due to an increase in electric components.Conventionally, materials with excellent visibility (transparency) andheat resistance have been used for the housings of the fuses inautomobiles. Polyethersulfone is one such material that has been used.

In recent years, the elevation of battery voltage for automobiles hascome under review. For example, the adoption of 42V systems is now beingdiscussed. However, the conventionally used polyethersulfone has poorarc resistance in 42V electric systems.

As substitute resins for polyethersulfone, crystalline polyamides suchas nylon 6 and nylon 66 have excellent arc resistance, however, they areinferior to conventional materials in heat resistance and transparency.There is a known technology to mix fibrous reinforcing materials such asglass fibers or mineral reinforcing materials such as calcium carbonateand talc to enhance heat resistance. However, it is inevitable thattransparency deteriorates in the polyamide resins mixed with thesereinforcing materials because the light reflects diffusely due to thereinforcing materials dispersed in the polyamide resins.

Meanwhile, there is a known technology to reduce the crystallineproperty of polyamides by copolymerization to improve the transparencyof polyamide resins. The technology is widely used in films wheretransparency is required. However, if the crystalline property isreduced, it is inevitable that strength and heat resistance deteriorate.The strength and the heat resistance can be enhanced by mixing thereinforcing materials as shown above. However, this is inevitablysacrifices the transparency to a large degree.

As a solution, there is a proposal that inorganic crystal componentswhich are significantly finer than the conventional reinforcingmaterials are evenly dispersed in the polyamide. For example, theJapanese Patent Laid-Open No. HEI5-339498 (1993-339498) andNo.2001-2913propose the polyamide resin compositions with excellenttransparency and surface glaze made by dispersing phyllosilicate incopolymer polyamide resins. Though these copolymer polyamides haveexcellent transparency, they have problems in heat resistance.Therefore, they can not be used in high temperature environment such asengine rooms of automobiles for long periods of time.

SUMMARY OF THE INVENTION

The purpose of the present invention is to offer a fuse for anautomobile with heat resistance that can be used in the high temperaturesuch as engine rooms of automobiles, transparency that enables theinside of the molded components to be seen and arc resistance. A fusefor an automobile in the present invention to achieve the purposes shownabove has a housing manufactured by the injection molding of a polyamideresin composition, wherein the polyamide resin composition constitutingthe housing has a heat of fusion of 40 J/g or more, as measured by meansof a differential scanning calorimeter, and exhibits an average diameterof spherulites of 0.51 μm or less, as measured by the observation bymeans of a polarization optical microscope.

Thus, it is possible to simultaneously enhance the heat resistance,transparency and arc resistance of the housing and, especially, maintainhigh transparency even when the fuse is used in high temperatures ofengine rooms of automobiles by forming the housings with polyamide resincompositions having a specific degree of crystallization and diameter ofspherulites.

The fuse for the automobile according to the present invention, morepreferably, shall be configured so that:

-   -   (1) the rate of change in the heat of fusion when heat-treating        at 130° C. for 30 minutes a polyamide resin composition molded        body that forms the housing obtained by injection-molding at a        mold temperature of 40° C. is less than 15%,    -   (2) the total light transmittance of a polyamide resin        composition molded body that forms the housing obtained by        injection-molding at a mold temperature of 70° C. is 80% or more        compared to the total light transmittance of a molded body        obtained by injection-molding at a mold temperature of 40° C.,    -   (3) the polyamide resin composition forming the housing is        composed of polyamide resin (a) and swellable phyllosilicate        (b),    -   (4) the polyamide resin (a) is at least one from group of nylon        6, nylon 66 and copolymer or mixture of the two,    -   (5) the polyamide resin is specifically nylon 6,    -   (6) the polyamide resin (a) is composed of a mixture of        crystalline polyamide (c) and low-crystalline or amorphous        polyamide (d),    -   (7) the exchangeable cations existing between the layers of the        swellable phyllosilicate (b) are swellable phyllosilicate        exchanged with organic onium ions,    -   (8) the swellable phyllosilicate (b) is montmorillonite,    -   (9)the swellable phyllosilicate (b) is dispersed in the        polyamide resin compositions on the monolayer level,    -   (10) the polyamide resin composition includes a crystal        nucleating agent (e), and    -   (11) the swellable phyllosilicate (b) is introduced in the        polyamide resin composition by using a melt kneading method.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawing is a perspective view of an example of the fuse for theautomobile according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The size and shape of the fuse for the automobile according to thepresent invention are not particularly limited if it is used on the wayof the electric components of automobiles. However, at least a part ofthe housing shall be injection-molded with a polyamide resin compositionwith a specific heat of crystal melting and diameter of spherulites asdescribed below.

A fuse 1 for an automobile shown in the drawing is composed of a housing2 injection-molded with a polyamide resin composition with a specificheat of crystal melting and a diameter of spherulites as describedabove, and a pair of terminal 3 and 4 inserted into the housing 2. Thehousing 2 has heat resistance to make the fuse usable for long periodsof time, transparency to make the inside of molded components visible,and arc resistance even in the high-temperature environment of theengine rooms of automobiles because the housing is composed of thepolyamide resin composition with the specific heat of crystal meltingand the diameter of spherulites.

The polyamide resin composition constituting the housing has the heat offusion of 40 J/g or more, preferably, 50 J/g or more, as measured bymeans of a differential scanning calorimeter (DSC) at a heating rate 10°C./min. If the heat of fusion is 40 J/g or less, the transparency maydeteriorates or the fuse may be deformed in higher temperature for longterm use. The upper value of the heat of fusion is not particularlylimited. However, it is preferably 70 J/g or less.

In this case, the heat of fusion of the polyamide resin composition isthe value by means of DSC measurements after a vacuum drying at 80° C.for more than 10 hours if the housing absorbed water.

The average diameter of spherulites of the polyamide resin compositionforming the housing is required to be 0.5 μm or less, preferably, 0.3 μmor less. If the diameter of spherulites exceeds 0.5 μm, the transparencydeteriorates because the light reflects diffusely due to thespherulites. The lower value of the diameter of spherulites is notparticularly limited. However, generally, it is desirable to set thelimit to about 0.01 μm. The diameter of spherulites used here is thevalue that is obtained by averaging the diameters of spherulites with animage analysis device after cutting ultra-thin sections from the housingcomposed of the polyamide resin composition, observing the sections witha polarization microscope or a transmission electron microscope andtaking pictures of the spherulites.

In the present invention, the rate of change in the heat of fusion ismore preferably is less than 15% between immediately after obtaining thehousing by injection molding a polyamide resin composition at moldtemperature of 40° C. and after heat treating the housing at 130° C. for30 minutes.

The polyamide resin composition used for the fuse for the automobileaccording to the present invention is not limited if it has the specificheat of fusion and size of spherulites. More specifically, the polyamideresin composition is preferably composed of polyamide resin (a) andswellable phyllosilicate (b).

The polyamide resin (a) used in the present invention is a copolymerwith amide bond primarily made from amino acid, lactam or diamine andcarboxylic acid. The polyamide resin (a) is not particularly limited.Polyamides made from any amino acids, lactam or diamine and carboxylicacids can be used. Specifically, the main component is preferablycrystalline polyamide resin (c).

The crystalline polyamide (c) means a crystalline polyamide with a heatof fusion of 30 J/g or more measured at heating rate 10° C./min with adifferential scanning calorimeter (DSC). Polyamide resins are notparticularly limited if they have the crystalline properties shownabove.

Specific examples of the starting materials include amino acids such as6-aminocaproic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid,para-aminomethylbenzoic acid, etc.; lactams such as e-caprolactam,ω-laurolactam, etc.; aliphatic, alicyclic or aromatic diamines such astetramethylenediamine, hexamethylenediamine,2-methylpentamethylenediamine, undecamethylenediamine,dodecamethylenediamine, 2,2,4-/2,4,4-trimethylhexamethylenediamine,5-methylnonamethylenediamine, metaxylylenediamine, paraxylylenediamine,1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane,1-amino-3-aminomethyl- 3,5,5-trimethylcyclohexane,bis(4-aminocyclohexyl)methane, bis(3-methyl-4-aminocyclohexyl)methane,2,2-bis(4-aminocyclohexyl)propane, bis(aminopropyl)piperazine,aminoethylpiperazine, etc.; aliphatic, alicyclic or aromaticdicarboxylic acids such as adipic acid, suberic acid, azelaic acid,sebacic acid, dodecane-diacid, terephthalic acid, isophthalic acid,2-chloroterephthalic acid, 2-methylterephthalic acid,5-methylisophthalic acid, 5-sodium-sulfoisophthalic acid,hexahydroterephthalic acid, hexahydroisophthalic acid, etc.

In the present invention, a polyamidehomopolymer or a copolymer derivedfrom these materials alone or mixture thereof may be used.

The crystalline polyamide resins preferably used in this invention ispolyamide resins with the melting point of 200° C. or higher. The moldedbodies obtained by using these polyamides can have excellent heatresistance and strength. Specific examples of polyamide resins includepolycaproamide (nylon 6), polyhexamethylene adipamide (nylon 66),polycaproamide/ polyhexamethylene adipamide copolymer (nylon 66/6),polytetramethylene adipamide (nylon 46), polyhexamethylene sebacamide(nylon 610), polyhexamethylene decamide (nylon 612),polyhexamethyleneterephtalamide/polydodecamide copolymer (nylon 6T/12),polyhexamethylenadipamide/polyhexamethylene terephthalamide copolymer(nylon 66/6T), and their mixtures and copolymers. Of those, preferredare nylon6, nylon 66, nylon 6/66 copolymers, etc.

The degree of polymerization of crystalline polyamides is not limitedspecifically if normal molding processes are possible. However, it ispreferable that the relative viscosity of polyamide resin 1% by weightmeasured in 98% concentrated sulfuric acid solution at 25° C. is in therange from 2.0 to 4.0.

According to the present invention, the polyamide resin (a) ispreferably a mixture of crystalline polyamide (c) and low-crystalline oramorphous polyamide (d).

The low-crystalline or amorphous polyamide (d) mean low-crystallinepolyamides where the difference (Tm-Tc) between the melting point (Tm)measured at a heating and cooling rate of 10° C./min with a differentialscanning calorimeter (DSC) and the crystallization temperature (Tc) atcooling is 40° C. or more, or amorphous polyamides where a heat offusion measured at a heating rate 10° C./min with a differentialscanning calorimeter is under 4 J/g.

The types of low crystalline or amorphous polyamides are notparticularly limited. Polyamides made from any amino acids, lactam ordiamine and dicarboxylic acid can be used. Specific examples of thestarting materials include amino acids such as 6-aminocaproic acid,11-aminoundecanoic acid, 12-aminododecanoic acid,para-aminomethylbenzoic acid, etc.; lactams such as e-caprolactam,ω-laurolactam, etc.; aliphatic, alicyclic or aromatic diamines such astetramethylenediamine, hexamethylenediamine,2-methylpentamethylenediamine, undecamethylenediamine,dodecamethylenediamine, 2,2,4-/2,4,4-trimethylhexamethylenediamine,5-methylnonamethylenediamine, metaxylylenediamine, p araxylylenediamine,1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane,1-amino- 3-aminomethyl-3,5,5-trimethylcyclohexane,bis(4-aminocyclohexyl)methane, bis(3-methyl-4-aminocyclohexyl)methane,2,2-bis(4-aminocyclohexyl)propane, bis(aminopropyl)piperazine,aminoethylpiperazine, etc.; aliphatic, alicyclic or aromaticdicarboxylic acids such as adipic acid, suberic acid, azelaic acid,sebacic acid, dodecane-diacid, terephthalic acid, isophthalic acid,2-chloroterephthalic acid, 2-methylterephthalic acid,5-methylisophthalic acid, 5-sodium-sulfoisophthalic acid,hexahydroterephthalic acid, hexahydroisophthalic acid, etc.

Of those, polyamides including compounds as raw materials havingaromatic rings or alicyclic structure such as terephthalic acids,isophthalic acids, metaxylylenediamine, paraxylylenediamine,bis(4-aminocyclohexyl)methane, bis(3-methyl-4-aminocyclohexyl)methaneare preferred.

In the present invention, particularly the useful low-crystalline oramorphous polyamides are those that have aromatic rings or alicyclicstructure units in the principal chain. The specific examples of theminclude polymethaxylylene adipamide (nylon MXD 6), polyhexamethyleneadipamide/polyhexamethyleneisophthalamide copolymer (nylon 66/6I),polycaproamide/polyhexamethyleneisophthalamide copolymer (nylon 6/6I),polyhexamethyleneterephthalamide/polyhexamethyleneisophthalamidecopolymer (nylon 6T/61), polyhexamethyleneadipamide/polyhexamethyleneterephthalamide/polyhexamethyleneisophthalamidecopolymer (nylon66/6T/6I), polyhexamethyleneadipamide/polyhexamethyleneisophthalamide/polycaproamide polymer(nylon66/6I/6) andpolyhexamethyleneterephthalamide/polyhexamethyleneisophthalamide/polyhexamethyleneadipamide copolymer (nylon6T/6I/66), etc.

Among them, nylon 66/6I and nylon 66/6I/6, etc are the most preferable.

The low-crystalline or amorphous polyamides (b) used in the presentinvention preferably include 3 to 30% by weight ofhexamethyleneisophthalamide unit, and more preferably, 10 to 20% byweight.

If the polyamide used in the present invention is composed of a mixtureof two or more polyamides, 1 to 20% by weight, and preferably 2 to 15%the hexamethyleneisophtalamide unit should be included in the mixture oftwo or more polyamides. The more preferable polyamide is a copolymerizedpolyamide including 3 to 30% by weight of hexamethyleneisophthalamideunit and 70 to 97% by weight of hexamethyleneadibamide unit. The furtherpreferable polyamide is a copolymerized polyamide composed of 3 to 30%by weight of hexamethylenephthalamide unit and 60 to 96% by weight ofhexamethyleneadipamide unit and 1 to 10% by weight of caproamide unit.

The degree of polymerization of low-crystalline or amorphous polyamidesis not limited specifically if normal molding processes are possible.However, it is preferable that the relative viscosity of a polyamideresin 1% by weight measured in 98% concentrated sulfuric acid solutionat 25° C. is in the range from 2.0 to 4.0.

In the polyamide resin used in this prevention, with regard to themixing ratio of the crystalline polyamide (c) and the low-crystalline oramorphous polyamide (d), when the total polyamide resin component is100% by weight, the crystalline polyamide (c) is 70 to 100% by weight,or preferably 80 to 95% by weight, and low-crystalline or amorphouspolyamide (d) is 0 to 40% by weight or preferably 5 to 20% by weight.Higher balances between heat resistance and transparency can beestablished by using a low-crystalline or amorphous polyamide (d) incombination with a crystalline polyamide (c).

The swellable phyllosilicate used as component (b) in this invention has2:1 structure where an octahedral sheet including metals such asaluminum, magnesium, lithium, etc is sandwiched between two silicatetetrahedral sheets to form a plate crystal layer. In general, there areexchangeable positive ions between layers of the plate crystal layer.

In general, the size of a plate crystal is 0.05 to 0.5 μm in width and 6to 15 angstrom in thickness. The cation-exchange capacity of theexchangeable cation is 0.2 to 3 meq/g, and preferably 0.8 to 1.5 meq/g.

Specific examples of the phyllosilicate include a smectites clay mineralgroup such as montmorillonite, beidellite, nontronite, saponite,hectorite and sauconite; a clay mineral group such as vermiculite,halloysite, kanemite, kenyte, zirconium phosphate, titanium phosphate; aswellable mica group such as Li-fluoro taeniolite, Na-fluoro teniolite,Na-fluoro-mica tetrasilicide, Li-fluoro-mica tetrasilicide, etc. Thesemay be a natural or synthesized.

Of those, a smectites clay mineral group such as montmorillonite andhectorite, a swellable mica group such as Na-fluoro-mica tetrasilicideand Li-fluoro taeniolite are preferable. Especially, montmorillonite isthe most preferable.

In this invention, a phyllosilicate where exchangeable positive ionsexisting between layers are exchanged with organic onium ions ispreferably used.

Organic onium ions usable here include ammonium ion, phosphonium ion,sulfonium ion, etc. Of those, ammonium ion and phosphonium ion arepreferably used. Ammonium ion may be any one of primary, secondary,third and quaternary ammonium.

Primary ammonium ions include decyl ammonium, dodecyl ammonium,octadecyl ammonium, oleyl ammonium and benzyl ammonium, etc.

Secondary ammonium ions include methyldecyl ammonium, methyldodecylammonium and methyloctadecyl ammonium, etc.

Third ammonium ions include dimethyldodecyl ammonium anddimethyloctadecyl ammonium etc.

Quaternary ammonium ions include benzyltri alkyl ammonium ions such asbenzyltrimethyl ammonium, benzyltriethyl ammonium, benzyltributylammonium, benzyldimethyldecyl ammonium, benzyldimethyloctadecylammonium; alkyltrimethyl ammonium ions such as trimethyloctyl ammonium,trimethldodecyl ammonium, trimethyloctadecyl ammonium; dimethyldialkylammonium ions such as dimethyloctyl ammonium, dimethyldodecyl ammonium,dimethyldioctadecyl ammonium; trialkylmethylammonium ions such astrioclylmethyl ammonium, tridodecylmethyl ammonium, etc.

In addition to them, ammonium ion derived from aniline,p-phenylenediamine, a-naphthylamine, p-aminodimethylaniline, penzidine,pyridine, piperidine 6-aminocaproic acid, 11-aminoundecanoic acid,12-aminododecanoic acid or the like may be included.

Of those ammonium ions, quaternary ammonium ions are preferable.Specific examples inlcude ammonium ions derived fromtrioctylmethylammonium, trimethyloctadecyl ammonium,benzyldimethyloctadecyl ammonium and 12-aminododecanoic acid.Especially, trioctylmethyl ammonium and benzyldimethyl ammonium are themost preferable.

In the present invention, the phyllosilicate where the exchangeablecations existing between layers are exchanged with organic onium ionscan be manufactured by reacting the phyllosilicate having exchangeablecations between layers with the organic onium ions by known methods.Specifically, the methods include a method by the ion-exchange reactionin the polar solvents such as water, methanol, ethanol, and methods tomake the liquid or the dissolved ammonium salt react with thephyllosilicate directly.

With regard to the amount of organic onium ions to the phyllosilicate inthe present invention, from the viewpoints of dispersibility ofphyllosilicate, thermal stability when, melted, gas when molded,suppression of odor developoment, etc, the amount of organic onium ionsis, in general, 0.4 to 2.0 equivalent weight to the cation exchangecapacity of phyllosilicate. Particularly, 0.8 to 1.2 equivalent weightis preferable.

These phyllosilicates are preferably used by preliminary treatments withcoupling agents having reactive functional groups as well as the organiconium salts shown above to obtain better mechanical strength.

These coupling agents include isocyanate compounds, organic silanecompounds, organic titanate compounds, organic borane compounds, epoxycompounds, etc.

As the coupling agent, preferred are organic silane compounds (silanecoupling agents), and their specific examples include epoxy group-havingalkoxysilane compounds such as y-glycidoxypropyltrimethoxysilane,y-glycidoxypropyltriethoxysilane,β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, etc.; mercaptogroup-having alkoxysilane compounds such asy-mercaptopropyltrimethoxysilane, y-mercaptopropyltriethoxysilane, etc.;ureido group-having alkoxysilane compounds such asy-ureidopropyltriethoxysilane, y-ureidopropyltrimethoxysilane,y-(2-ureidoethyl)aminopropyltrimethoxysilane, etc.; isocyanatogroup-having alkoxysilane compounds such asy-isocyanatopropyltriethoxysilane, y-isocyanatopropyltrimethoxysilane,y-isocyanatopropylmethyldimethoxysilane,y-isocyanatopropylmethyldiethoxysilane,y-isocyanatopropylethyldimethoxysilane,y-isocyanatopropylethyldiethoxysilane, etc.; amino group-havingalkoxysilane compounds such asy-(2-aminoethyl)aminopropylmethyldimethoxysilane, y-(2-aminoethyl)aminopropyltrimethoxysilane,y-aminopropyltrimethoxysilane, etc.; hydroxyl group-having alkoxysilanecompounds such as y-hydroxypropyltrimethoxysilane,y-hydroxypropyltriethoxysilane, etc.; carbon-carbon unsaturatedgroup-having alkoxysilane compounds such asy-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane,N-β-(N-vinylbenzylaminoethyl)-y-aminopropyltrimethoxysilanehydrochloride, etc. Especially preferred are carbon-carbon unsaturatedbond-having alkoxysilane compounds.

For processing phyllosilicates with any of these coupling agents, amethod of making the phyllosilicate absorb a coupling agent in a polarsolvent of water, methanol, ethanol or the like or in a mixed solventthereof, a method of making the phyllosilicate adsorb a coupling agentby dropping the agent with stirring the phyllosilicate in a high-speedstirring mixer such as a Henschel mixer; or a method of making thephyllosilicate adsorb the silane coupling agent by adding the agent tothe phyllosilicate directly and mixing them in a mortar or the like: anyof above methods can be used. While phyllosilicates are processed with acoupling agent, it is desirable to mix water, acidic water, alkalinewater or the like at the same time so as to promote the hydrolysis ofthe alkoxy group in the coupling agent. In this case, in addition towater, an organic solvent such as methanol, ethanol or the like capableof dissolving both water and the coupling agent may be added to thesystem to increase the reactivity of the coupling agent. Heating thephyllosilicates processed with the coupling agent in this way makespossible to promote its reaction further.

When manufacturing the compounds in the present invention by melting andkneading phyllosilicates and polyamide resins, without previouslyprocessing phyllosilicates with a coupling agent, an integral blendingmethod of adding these coupling agents in melting and kneading thephyllosilicate and the polyamide resin may be used.

In the invention, the order of the step of processing phyllosilicateswith organic onium ions and the step of processing them with a couplingagent is not specifically defined. However, following processingphyllosilicates first with organic onium ions, processing them with acoupling agent is preferable.

The amount of the swellable phyllosilicate (b) of the invention may fallin the range from 0.1 to 20% by weight in terms of the amount of theinorganic ash content of the polyamide resin composition of theinvention, but preferably in the range from 0.5 to 15% by weight. Evenmore preferably, it falls in the range from 1 to 10% by weight. If theamount of the ash content is too small, the heat resistance and thetransparency of the molded products may degrade. If the amount of theash content is too large, the toughness may degrade. The amount of theinorganic ash content may be determined by ashing 2 g of the polyamideresin composition in an electric furnace at 600° C. for 3 hours.

In the polyamide resin composition used in the present invention,the_phyllosilicates are preferably dispersed evenly in the polyamideresin composition as a matrix on the monolayer level. The dispersionevenly in the monolayer level means that the phyllosilicates aredispersed entirely in the matrix resin in one to ten layers or sowithout secondary aggregations. The state can be confirmed by cuttingsamples from the polyamide resin composition and observing them with anelectron microscope.

The polyamide resin composition used in the invention may be optionallyadded a crystal nucleating agent (e) to in order to regulate thecrystallinity. The crystal nucleating agents are not limited. Specificexamples include inorganic particles such as talc, silica, graphite;metal oxides such as magnesium oxide and aluminum oxide;polyamideoligomer such as caprolactam duplicitas; high-melting pointpolyamides such as nylon 6T, nylon 66/6T, etc.

Of those, inorganic particles such as talc, silica, etc are preferable.Talc is still preferable. If the crystal nucleating agent is added, theamount of one, preferably falls in the range from 0.01 to 10 parts byweight, more preferably in the range from 0.03 to 5 parts by weight,further preferably in the range from 0.05 to 3 parts by weight relativeto 100 parts by weight of the polyamide resin composition.

The polyamide resin composition of the invention may be optionally addedany known additives of, in the range that they do not impair the effectsof the present invention, for example, antioxidants and heat-resistingagents (hindered phenol system stabilizer, hydroquinone systemstabilizer, phosphite system stabilizer, and these substitutedstabilizers, etc.), to prevent yellowing or discoloration phosphoruscompounds, weather-resistant agents (resorcinol system stabilizer,salicylate system stabilizer, benzotriazole system stabilizer,benzophenone system stabilizer, hindered amine system stabilizer, etc.),mold-releasing agents and lubricants (montanic acid and its metal salts,its esters, its half esters, stearyl alcohol, stearamide, variousbisamides, bisurea, polyethylene wax, etc.), pigment (cadmium sulfide,Phthalocyanine, carbon black, metallic pigments, etc.), dye (Nigrosine,etc.), plasticizers (p-oxybenzoic acid octyl,N-butylbenzenesulfoneamide, etc), antistatic agents (nonionic antistaticagents such as alkyl sulphate anion antistatic agents, quaternaryammonium salt cation antistatic agents, polyoxyethylene sorbitanmonostearate; betaine amphoteric antistatic agents, etc), fireretardants (red phosphorus, melaminecyanolate, hydroxides such asmagnesium hydrate, aluminum hydroxide, etc., ammonium polyphosphate,brominated polystylene, brominated PPO, brominated PC, brominated epoxyresin or combinations of these bromine system fire retardants andantimon trioxide), other polymer (polyester, polycarbonate,polyphenylene ether, polyphenylene sulfide, polyether sulfone, ABSresin, SAN resin, polystyrene, acrylic resin, polyethylene,polypropylene, SBS, SEBS, varied elastomers, etc.).

The methods to obtain the polyamide resin compounds used in the presentinvention are not particularly limited. For example, phyllosilicates mayexist when polymerizing polyamides but more preferable method is tomelt-blend polyamide resins and phyllosilicates. In this case, themethod to melt-blend polyamide resins and phyllosilicates are notparticularly limited if mechanical shearing is possible when polyamideresins are melted. The processing method may be either the batch processor continuous process. The continuous method to manufacture continuouslyis more preferable from the viewpoint of operating efficiency.

Although there is no limitation for a specific mixer in use, anextruder, especially, a twin screw extruder is preferable from aviewpoint of proficiency. In order to remove water and low molecularweight volatile substances which are generated during melt-blending,vent ports are preferably arranged. In the case a twin screw extruder isused, the supply method of materials and agents may be either bysupplying the mixture of polyamide resin (a) and phyllosilicate (b)mixed in a blender or the likes in advance from a feed port of theextruder, or by supplying polyamide resin (a) from a feed port upstreamof the extruder and a phyllosilicate (b) and crystal nucleating agents(e) from a feed port downstream of the extruder. The method to supply isnot particularly limited. The arrangement of screws of the extruder isnot also limited, but a kneading zone is preferably arranged to dispersephyllosilicate into a monolayer level.

In order to disperse phyllosilicate, after manufacturing a master batchby melt-blending a part of polyamide resin (a) and phyllosilicate (b),melt-blending again with the remainder of the polyamide is preferable.

The polyamide resin composition used in the present invention is usedfor forming a housing part of a fuse by injection-molding. Obtainedmolded products have excellent transparency and heat resistance. Themolded products of polyamide resin compositions according to the presentinvention can be processed afterward by cutting and varied welding.

As shown above, since the fuse for the automobile of the invention ismade with its housing parts formed by polyamide resin compositionshaving a specific degree of crystallization and diameter of spherulites,the heat resistance, transparency and arc resistance are excellent atthe same time, especially it is possible to prevent the transparencyfrom deteriorating by using even for a long period of time under hightemperature in an engine room of an automobile.

The invention is described more specifically with reference to thefollowing Examples, which, however, are not intended to restrict thescope of the invention. The evaluation items in the embodiments andcomparative examples were measured according to the methods mentionedbelow.

[Heat of crystal fusion(products molded at mold temperature 40° C.)]:

A part of thin and transparent areas of a fuse housing injection-moldedat mold temperature 40° C. was sampled and measured using a differentialscanning calorimeter (DSC) available from Seiko Instruments Inc. Theheat of fusion was also measured by the same method after heat-treatingthe molded samples shown above at 130° C. for 30 minutes.

[Diameter of spherulites]:

Ultra-thin sections were cut out from a thin and transparent part of thefuse housing. Using an image analysis device, average diameter ofspheruhites were calculated from the pictures of spherulites taken witha polarization optic microscope.

[Total light transmittance]

Total light transmittances of square plates with a size of 80 mm×80 mm×1mm (depth×width×thickness), which were injection-molded at moldtemperature of 40° C. and 70° C. respectively, were measured using adirect reading hazemeter available from Toyo Seiki Seisaku-Sho Ltd.Total light transmittances of molded plates obtained at mold temperatureof 40° C. were also measured in the same method after heat-treating at130° C. for 30 minutes.

[Load deflection temperature]:

Load deflection temperature was measured at a load of 0.46 MPa accordingto ASTM D648.

[Clay dispersibility ]

Ultra-thin samples were cut out from a thin and transparent part of thefuse housing to conduct visual evaluation of clay dispersibility using atransmission electron microscope.

The criteria for visual evaluation were as follows.

⊚:Clay is dispersed evenly in monolayer to several layers.

◯: Clay is dispersed evenly in monolayer to ten layers.

Δ: In some areas, clay is dispersed evenly in monolayer to ten layers.

However, aggregation of ten layers or more also exists.

x :Clay exists in aggregation of ten layers or more.

[Arc resistance]:

ASTM No.1 dumbbell test pieces were molded at mold temperature of 70° C.Arc resistance was measured using an arc resistance tester manufacturedby Tokyo Seiden Company Limited according to ASTM D495.

Reference example 1 (manufacturing of low-crystalline polyamide)

75 part by weight of equimolal salt of hexamethylenediamine and adipicacid, 20 part by weight of equimolal salt of hexamethylene diamine andisophthalic acid and 5 part of e-caprolactam by weight were put into areactor and then the same amount of pure water as all materials pouredin was added. After the reactor was well replaced with nitrogen, heatingwas started while stirring. The final target temperature was set to 270°C. adjusting the pressure in the reactor at a maximum 2.0 MPa. Thepolymer discharged into the water bath was pelletized with a strandcutter to obtain low-crystalline polyamide (d-1).

The relative viscosity of the obtained low-crystalline polyamide in aconcentrated sulfuric acid at 25° C. with a concentration of 1% was2.30. The melting point (Tm) and temperature-falling crystallizationtemperature (Tc) measured with a differential scanning calorimeter were233° C. and 176° C. respectively.

Reference example 2 (manufacture of swellable phyllosilicate)

After Na-montmorillonite (Kunimine Industries Co., Ltd.: Kunipia F,cation exchange capacity 120 m equivalent/100 g) of 100 g was put intoten liters of warm water to be stirred and dispersed, two liters of warmwater in which benzyldimethyloctadecylammonium chloride (equivalentamount of cation exchange capacity) of 51 g was dissolved was added toit and stirred for one hour. Generated precipitation was filtered andthen washed with warm water. After repeating the washing and thefiltration three times, obtained solid matter was vacuum-dried at 80° C.to obtain dried swellable phyllosilicate (b). The measurement value ofthe inorganic ash content of the obtained swellable phyllosilicate was68 weight %. The measurement value of the inorganic ash content wasobtained by ashing the swellable phyllosilicate of 0.1 g in an electricfurnace at 600° C. for 3 hours.

EXAMPLE 1

A polyamide (c-1: nylon 6 with a relative viscosity of 2.70 measured ata concentration of 1% in concentrated suluric acid at 25° C.) and 3 partof swellable phyllosilicate by weight (b) obtained in the referenceexample 2 were mixed and pre-blended with a tumbler mixer, then theywere melt-blended with TEX-30 twin screw extruder (The Japan SteelWorks, Ltd.) setting the cylinder temperature to 250° C. to obtainpolyamide resin composition.

Obtained polyamide resin composition was vacuum-dried at 8° C. for tenhours after being pelletized to injection-mold a fuse housing part andASTM test pieces shown in FIG. 1 at the cylinder temperature 250° C. andat mold temperature 40° C. and 70° C. respectively. Table 1 shows theevaluation results of properties of the fuse housing part and ASTM testpieces.

EXAMPLE 2

Except that 0.1 part of talc by weight as a crystal nucleating agent (e:LMS-300 by Fuji Talc Industrial Co., Ltd.) was added, a polyamide resincomposition was also prepared in the same manner as in Example 1 toinjection-mold a fuse housing part and ASTM test pieces. Table 1 showsthe evaluation results of them.

EXAMPLE 3

A resin composition was obtained from a polyamide (c-2: nylon 6/66copolymer with a relative viscosity of 2.75 measured at a concentrationof 1% in concentrated sulfuric acid at 25° C., nylon 6 content of 95weight %) and 3 part of swellable phyllosilicate by weight (b) obtainedin the reference example 2 in the same manner as in Example 1 toinjection-mold a fuse housing part and ASTM test pieces. Table 1 showsthe evaluation results of their properties.

EXAMPLE 4

Except that 0.1 part of talc by weight as a crystal nucleating agent (e:LMS-300 by Fuji Talc Industrial Co., Ltd.) was added, a polyamide resincomposition of Example 4 was prepared in the same manner as in Example 3to injection-mold a fuse housing part and ASTM test pieces. Table 1shows the evaluation results of their properties.

EXAMPLE 5

A polyamide resin composition was obtained in the same manner as inExample 1 from 90 part of polyamide by weight (c-1: nylon 6 with arelative viscosity of 2.70 measured at a concentration of 1% inconcentrated sulfuric acid at 25° C.), 10 part of low-crystallinepolyamide by weight (d-1) and 3 part of swellable phyllosilicate byweight (b) obtained in the reference example 2 to injection-mold a fusehousing part and ASTM test pieces. Table 1 shows the evaluation resultsof their properties.

EXAMPLE 6

Except that 0.1 part of talc by weight as a crystal nucleating agent (e:LMS-300 by Fuji Talc Industrial Co., Ltd.) was added, a polyamide resincomposition of Example 6 was prepared in the same manner as in Example 5to injection-mold a fuse housing part and ASTM test pieces. Table 1shows the evaluation results of their properties.

EXAMPLES 7-9

Except that each material was used with the blending ratio shown intable 1, a polyamide resin composition was obtained in the same manneras in Example 1 to injection-mold a fuse housing part and ASTM testpieces composition. Table 1 shows the evaluation results of theirproperties.

EXAMPLE 10

A resin composition was obtained to evaluate the properties in the samemanner as in Example 1 by compounding 100 part of polyamide resin byweight (c-1), 3 part of phyllosilicate by weight (b) and 0.5 part oftalc by weight as a crystal nucleating agent (e) used in the example 1and also 0.2 part of N, N′-hexamethylenebis(3,5-di-tert-butyl-4-hydrocinnamamide) by weight (Toray Fine ChemicalsCo., Ltd.) and 0.5 part of sodium hypophosphite by weight (Tokyo KaseiKogyo Co., Ltd.). According to the evaluation of the properties, thediameter of spherulites was 0.08 μm, heat of fusion (40° C. molding) was60 J/g, total light transmittance (initial value at 40° C.) was 90%,total light transmittance (during heat-treating) was 72%, loaddeflection temperature was 192° C. and arc resistance was 100 sec.

COMPARATIVE EXAMPLE 1

Except that a swellable phyllosilicate (b) was not compounded, apolyamide resin composition was obtained in the same manner as inExample 1 to injection-mold a fuse housing part and ASTM test pieces.Table 2 shows the evaluation results of their properties.

COMPARATIVE EXAMPLES 2-6

Except that each material used in examples was used with the blendingratio shown in table 2, a polyamide resin composition was obtained inthe same manner as in Example 1 to injection-mold a fuse housing partand ASTM test pieces. Table 2 shows the evaluation results of theirproperties.

COMPARATIVE EXAMPLE 7

Except that a swellable phyllosilicate (b) was not compounded, apolyamide resin composition was obtained in the same manner as inExample 8 to injection-mold a fuse housing part and ASTM test pieces.Table 2 shows the evaluation results of their properties.

Possibility for Industrial Use

The fuse for the automobile in the present invention can be used forvaried electric parts for automobiles in the automobile industry.Especially, it can be effectively used for electric parts in the enginerooms under high temperature atmosphere. TABLE 1 Exam- Exam- Exam- Exam-Exam- Exam- Exam- Exam- Exam- ple 1 ple 2 ple 3 ple 4 ple 5 ple 6 ple 7ple 8 ple 9 Polyamide (c-1) part by weight 100 100 90 90 80 90 90Polyamide (c-2) part by weight 100 100 Polyamide (c-3) part by weight 1010 20 10 10 (b) Swellable phyllosilicate part by weight 3 3 3 3 3 3 3 510 (e) Talc part by weight 0.1 0.1 0.1 Diameter of spherulites μm 0.080.08 0.08 0.1 0.08 0.08 0.1 0.2 0.2 Heat of fusion 40° C. molding J/g 5360 48 50 50 53 44 51 51 Heat-processing J/g 56 63 50 51 52 54 47 52 51Total light Initial value at 40° C. % 90 88 93 91 95 93 97 88 87transmittance Heat-processing % 88 80 90 90 90 86 93 86 86 Moldtemperature 70° C. % 84 82 86 85 88 86 90 83 81 Deflection temperatureunder load ° C. 190 192 180 182 185 188 181 189 193 Dispersibility ofclay ⊚ ⊚ ⊚ ◯˜⊚ ⊚ ⊚ ◯˜⊚ ◯ ◯ Arc resistance sec 102 100 103 102 105 100103 100 100

TABLE 2 Compara- Compara- Compara- Compara- tive tive tive tiveComparative Comparative Comparative example 1 example 2 example 3example 4 example 5 example 6 example 7 Polyamide (c-1) part by weight100 100 90 80 20 20 Polyamide (c-2) part by weight 100 Polyamide (c-3)part by weight 10 20 80 80 (b) Swellable phyllosilicate part by weight 3(e) Talc part by weight 3 Diameter of spherulites μm 2 2 1.5 1.5 1.3 0.80.5 Heat of fusion 40° C. molding J/g 70 65 43 40 40 36 38Heat-processing J/g 72 66 52 46 46 43 45 Total light Initial value at40° C. % 55 55 68 90 92 97 95 transmittance Heat-processing % 42 40 6070 72 82 82 Mold temperature 70° C. % 50 48 63 84 86 90 88 Deflectiontemperature under load ° C. 177 190 170 170 168 150 155 Dispersibilityof clay — — — — — — ◯˜Δ Arc resistance sec 110 98 100 110 105 95 95

1. A fuse for an automobile comprising a housing manufactured by theinjection molding of a polyamide resin composition, wherein thepolyamide resin composition constituting the housing has a heat offusion of 40 J/g or more, as measured by means of a differentialscanning calorimeter, and exhibits an average diameter of spherulites of0.5 μm or less, as measured by the observation by means of apolarization optical microscope.
 2. A fuse for an automobile accordingto claim 1, wherein the rate of change in the heat of fusion, whenheat-treating at 130° C. for 30 minutes a polyamide resin compositionmolded body that forms the housing obtained by injection-molding at amold temperature of 40° C., is less than 15%.
 3. A fuse for anautomobile according to claim 1, wherein the total light transmittanceof a polyamide resin composition molded body that forms the housingobtained by injection-molding at a mold temperature of 70° C. is 80% ormore compared to the total light transmittance of a molded body obtainedby injection-molding at a mold temperature of 40° C.
 4. A fuse for anautomobile according to claim 1, wherein a polyamide resin compositionforming the housing is composed of a polyamide resin (a) and a swellablephyllosilicate (b).
 5. A fuse for an automobile according to claim 4,wherein said polyamide resin (a) is at least one from the group of nylon6, nylon 66 and copolymer or mixture of the two.
 6. A fuse for anautomobile according to claim 5, wherein said polyamide resin (a) isnylon
 6. 7. A fuse for an automobile according to claim 4, wherein saidpolyamide resin (a) is composed of a mixture of crystalline polyamide(c) and low-crystalline or amorphous polyamide (d).
 8. A fuse for anautomobile according to claim 4, wherein the exchangeable positive ionsexisting between the layers of said swellable phyllosilicate (b) areswellable phyllosilicate exchanged with organic onium ions.
 9. A fusefor an automobile according to claim 4, wherein said swellablephyllosilicate (b) is montmorillonite.
 10. A fuse for an automobileaccording to claim 4, wherein said swellable phyllosilicate (b) isdispersed in the polyamide resin compositions on the monolayer level.11. A fuse for an automobile according to claim 4, wherein saidpolyamide resin composition includes a crystal nucleating agent (e). 12.A fuse for an automobile according to claim 4, wherein said swellablephyllosilicate (b) is introduced in the polyamide resin composition byusing a melt kneading method.
 13. A fuse for an automobile according toclaim 2, wherein the total light transmittance of a polyamide resincomposition molded body that forms the housing obtained byinjection-molding at a mold temperature of 70° C. is 80% or morecompared to the total light transmittance of a molded body obtained byinjection-molding at a mold temperature of 40° C.
 14. A fuse for anautomobile according to claim 2, wherein a polyamide resin compositionforming the housing is composed of a polyamide resin (a) and a swellablephyllosilicate (b).
 15. A fuse for an automobile according to claim 3,wherein a polyamide resin composition forming the housing is composed ofa polyamide resin (a) and a swellable phyllosilicate (b).
 16. A fuse foran automobile according to claim 13, wherein a polyamide resincomposition forming the housing is composed of a polyamide resin (a) anda swellable phyllosilicate (b).